The present invention relates to a fluid pressure-driven combination actuator which is used for carrying a workpiece, assembly operation, and the like and in which linear reciprocating motion and rotating swinging motion are combined and more specifically to a combination actuator with a speed variable mechanism in which speeds of both linear motion and swinging are variable.
Conventionally, a fluid pressure-driven combination actuator for combining and outputting swinging motion and linear motion generally has a basic structure in which a swinging actuator for swinging and rotating an output shaft and a linear cylinder for linearly driving the output shaft are combined. This structure is formed by merely connecting a linear actuator and the swinging actuator which can be driven independently, which hinders miniaturization of the actuator, simplification of a fluid pressure control circuit, reduction of manufacturing cost, and the like. In the above structure, because two or more solenoid valves for driving both the actuators are necessary, much electrical energy and fluid pressure energy are consumed, which hinders energy conservation.
To cope with the above problems, the present inventors proposed, in Japanese Patent Application No. 11-33316, a combination actuator in which two motions, i.e., swinging and linear motion were carried out by one fluid pressure driving system. Although this combination actuator is superior to the above prior-art in that the one fluid pressure driving system (cylinder) is used, a swinging speed of the actuator is restricted by a linear motion speed by the fluid pressure driving system because there is only one fluid pressure driving system and therefore, it is impossible to satisfy demand to individually and arbitrarily adjust the swinging speed and the linear motion speed.
Furthermore, if efforts are made to make it possible to arbitrarily adjust the swinging speed and the linear motion speed by separate actuators, a shock is generated at each motion end to hinder carrying and assembly operations and it is necessary to give consideration to prevention of such a problem.
The present invention has been accomplished to solve the above problems and it is a technical object of the invention to make it possible to individually adjust driving speeds of linear motion and swinging in a combination actuator in which two motions, i.e., the linear motion and swinging can be carried out easily and at low cost by one fluid pressure driving system.
It is another technical object of the invention to provide a combination actuator with a speed variable mechanism in which connection of the linear motion and swinging motion can be achieved with a slight shock.
To achieve the above objects, in a combination actuator of the invention, an output shaft is connected to a piston rod of a fluid pressure-driven liner cylinder through a converting mechanism for converting linear thrust of the piston rod into rotational torque, the output shaft is caused to carry out linear motion and swinging rotation by controlling converting operation of the converting mechanism by operation setting means having a cam groove and a cam follower, and a driving speed of a piston can be changed by adjusting fluid pressure acting on the piston in a linear motion area and a swinging area of the output shaft respectively.
Because the output shaft is coaxially connected to the piston rod of the linear cylinder through a converting mechanism for converting in the combination actuator of the invention with the above structure, the structure can be simplified as compared with the prior-art combination actuator, the number of parts can be reduced, the actuator can be miniaturized, and manufacturing cost can be reduced. Because it is possible to cause the output shaft to carry out necessary combination operation by merely driving the linear cylinder, it is possible to easily control driving of linear motion and swinging by one fluid pressure driving system at low cost. Furthermore, because driving speeds of the linear motion and swinging can be adjusted individually and the driving speed of the piston is changed rapidly but continuously, it is possible to connect the linear motion and swinging motion with a slight shock.
In the invention, the converting mechanism includes a spiral groove provided to one of the piston rod and the output shaft and a connecting member which is provided to the other of the piston rod and the output shaft and which can rotate along the spiral groove.
The speed changing means preferably includes a recessed portion and a throttle for connecting a rod-side pressure chamber of the piston and a port substantially in parallel and means for separating the recessed portion and the rod-side pressure chamber from each other immediately before the piston reaches the swinging area from the linear motion area. The separating means is preferably formed of packing mounted to an inner peripheral face of the recessed portion and a valve ring fitted over an outer periphery of the rod and airtightly fitted into the packing.
According to a concrete embodiment of the invention, a first opening constantly communicating with the rod-side pressure chamber and a second opening in a position corresponding to a boundary between the swinging area and the linear motion area are provided to a bore face of the cylinder bore, the first opening is connected to the port through a check valve for preventing backflow of fluid from the rod-side pressure chamber toward the port, and the second opening is connected to the port through a check valve for preventing backflow of fluid from the cylinder bore toward the port and a throttle for restricting a flow rate of fluid flowing from the port into the cylinder bore.
According to another concrete embodiment of the invention, the packing has a function as a check valve for preventing a flow of fluid from the rod-side pressure chamber toward the port and for allowing a flow of fluid from the port toward the rod-side pressure chamber, an opening is provided in a position corresponding to a boundary portion between the swinging area and the linear motion area in a bore face of the cylinder bore, and the opening and the port are connected to each other through a check valve for preventing backflow of fluid from the cylinder bore toward the port and a throttle for restricting a flow rate of fluid flowing from the port into the cylinder bore.
The throttle is preferably a variable throttle an opening degree of which is adjustable and the driving speed of the piston can be adjusted by adjusting the opening degree.